This invention relates to a camshaft drive arrangement for an engine and more particularly to an improved compact highly serviceable camshaft drive arrangement for an engine.
As is well known, engines, particularly those employed in motor vehicles have become increasingly complex and complicated in nature. In addition to the complexity of the engine itself, the placement of the engine in the engine compartment has added further demands on the designer. Specifically, it is desirable to maintain a low hood line so as to improve wind resistance and fuel economy. However, this problem is greatly complicated by the complexity of the engine and its accessories and components. In addition to these problems, it is frequently the practice to place the engine transversely in the engine compartment and closely adjacent the axles which are driven by the engine. This gives rise to a number of additional problems.
As noted in our copending applications, certain advantages can be enjoyed by having the engine crankshaft drive an output shaft that is mounted to one side of the engine and which drives the axles on the other side of the engine. However, this type of drive arrangement may give rise to certain problems in connection with the camshaft drive of the engine. As noted in those aforenoted applications, the camshaft drive can be made more compact if the camshafts are driven in two stages from the engine output shaft via an intermediate shaft that is mounted adjacent the upper end of the cylinder block.
In connection with such a placement for the camshaft drive and intermediate shaft, however, certain additional problems are encountered. Specifically, it is desirable to place the drives in two different locations rather than have the two drive trains both located at the end of the engine and extending beyond it. That is, if the camshaft drive arrangements are located at the end of the engine and extend beyond the end, the overall engine length will be increased.
However, if part of the camshaft drive mechanism is located inwardly from the end of the engine, then additional problems are encountered. Specifically, if the camshaft drive is positioned between a pair of the cylinders, the drive mechanism for the camshaft may encroach into the cylinder block and the fastening arrangements between the cylinder block and the cylinder head. In addition, with cross flow cylinder heads the camshaft drive can also encroach on the porting associated with the engine.
It is, therefore, a principal object of this invention to provide an improved and compact camshaft drive arrangement for an engine.
It is a further object of this invention to provide a camshaft drive arrangement for an engine wherein the drive is accomplished in successive stages and at least a portion of the drive is not located at the extreme end of the engine.
It is a further object of this invention to provide a staged camshaft drive arrangement for an engine that will permit a compact construction and yet will not interfere with the other components of the engine.
In addition to the problems of placement of the camshaft drive already described, there is also the design factor that frequently it is necessary to access a portion of the camshaft drive mechanism for servicing purposes. That is, if the drive employs belts or chains, replacement of those components may be required. In addition, when servicing other components of the engine it may be necessary to access the camshaft drive so as to retime the camshafts relative to the engine crankshaft. By employing a staged camshaft drive of the type as aforedescribed, these accessibility problems also become more complicated.
It is, therefore, a still further object of this invention to provide a improved camshaft drive arrangement for an engine that permits a compact engine construction but which nevertheless is easily accessible for servicing.
When the engine is of the type of construction having the output shaft be a shaft other than the crankshaft of the engine, then that output shaft tends to be in a location in closer proximity to the camshaft drive arrangement. It is important, however, to be able to provide a large flywheel for the output shaft so as to accommodate a clutch or torque converter of adequately size to handle the power of the engine. However, if the camshaft drive is positioned in proximity to this end of the engine, then further enlargement of the flywheel may be hampered.
It is, therefore, a yet further object of this invention to provide an improved engine arrangement having an output shaft driven by the engine crankshaft and a camshaft drive arrangement that is positioned so that it will not interfere with the use of a large flywheel on the engine output shaft.